Hydroxy ethyl bibenzoate

ABSTRACT

New compounds including bis- beta -hydroxy ethyl bibenzoate containing less than 2.5%, and preferably less than 1%, diethylene glycol and a process for the production of the bis- beta -hydroxy ethyl bibenzoate by the condensation of 4,4&#39;-biphenyl dicarboxylic acid and ethylene glycol at low temperature and pressure in the presence of a catalyst are disclosed. Use of the compounds to produce polyesters is also disclosed.

BACKGROUND OF THE INVENTION

This invention relates to a new hydroxy thyl bibenzoate compound and amethod of producing the compound. More particularly, this inventionrelates to a hydroxy ethyl bibenzoate compound containing less than 2.5%diethylene glycol. More particularly, this invention relates to a newbis-β-hydroxy ethyl bibenzoate containing less than 2.5% diethyleneglycol, a method for making the compound and use of the compound in theproduction of polyesters.

DESCRIPTION OF THE PRIOR ART

Biphenyl dicarboxylic acid has been used as a monomer to producepolymers which may find use in high temperature applications. However,problems have been encountered in reducing undesired substituentsattached to the bibenzoate. The methyl or ethyl ester is used instead ofbiphenyl dicarboxylic acid to overcome its poor reactivity as biphenyldicarboxylic acid has a low solubility, a high melting point and meltingis accompanied by dis-association. The synthesis of methyl or ethylesters of biphenyl dicarboxylic acid is difficult, requiring hightemperature and pressure. Although the methyl ester of biphenyldicarboxylic acid can be produced from methanol and biphenyldicarboxylic acid using a catalyst, a good, safe commercial process hasnot been developed. Use of the ester also adds process steps to produceand purify the ester. A large portion of the production of polyethyleneterephthalate (PET) is based upon the use of terephthalic acid andethylene glycol, not the dimethyl terephthalate, so the inclusion ofanother comonomer in the form of the methyl ester of a dicarboxylic acidis undesirable. The inclusion of the methyl or ethyl ester of adicarboxylic acid results in the formation of methanol or ethanol whichis distilled off with the ethylene glycol during the production of thePET. The ethylene glycol cannot be recycled in this process withoutbeing purified to remove the methanol or ethanol byproduct, adding costand complexity to the process.

A need remains for a substantially pure, highly reactive material thatcan be used in processes based upon polyethylene terephthalate, dimethylterephthalate and terephthalic acid to improve the properties of thematerials.

SUMMARY OF THE INVENTION P It is an object of this invention to providea substantially pure hydroxy ethyl bibenzoate.

It is another object of this invention to produce bis-β-hydroxy ethylbibenzoate containing less than 2.5%, and preferably less than 1%,diethylene glycol.

It is a further object of this invention to provide a process for theproduction of bis-β-hydroxy ethyl bibenzoate containing less than 2.5%,and preferably less than 1%, diethylene glycol.

It is also an object of this invention to use the bis-β-hydroxy ethylbibenzoate in the production of polyesters.

These and other objects are met by this invention which is directed tothe production of bis-β-hydroxy ethyl bibenzoate containing less than2.5%, and preferably less than 1%, diethylene glycol. The bis-β-hydroxyethyl bibenzoate is produced by the condensation of 4,4'-biphenyldicarboxylic acid and ethylene glycol at low temperature and pressure inthe presence of a titanium based catalyst. The temperature of theprocess is preferably between about 180° C. and about 200° C., and ispreferably about 197° C., and the process pressure is approximatelyatmospheric pressure. Bis-β-hydroxy ethyl bibenzoate is homopolymerizedor copolymerized along with the condensation product of terephthalicacid and ethylene glycol in essentially the same manner as in theprocess for making polyethylene terephthalate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a substantially pure hydroxy ethylbibenzoate compound. For this application the term "substantially pure"means a compound in which few of the repeating units contain undesirablesubstituents. Thus the substantially pure hydroxy ethyl bibenzoate ofthis invention includes less than 2.5%. by weight diethylene glycol andpreferably it includes less than 1% by weight diethylene glycol. Apreferred compound is bis-β-hydroxy ethyl bibenzoate.

The preparation of hydroxy alkyl carboxylates such as, for example,bis-β-hydroxy ethyl bibenzoate produces diethylene glycol as a byproductand some of the diethylene glycol reacts to become a substituent on thecarboxylate Compound. It is believed that this reaction is acidcatalyzed. The inclusion of diethylene glycol as a substituent on thecarboxylate compound is undesirable when the carboxylate is incorporatedinto other compositions as the diethylene glycol acts to decrease theglass transition temperature (Tg), an effect opposite that generallydesired from the addition of the bibenzoate moiety.

Thus, the process of this invention which reduces the amount ofdiethylene glycol, and other similar substitUents, included in thehydroxy ethyl bibenzoate produces a bibenzoate that can be incorporatedin the production of other polymers or compositions without causingundesired effects. More specifically, the process of this inventionproduces a new compound, a bis hydroxy alkyl carboxylate and morespecifically a bis-β-hydroxy ethyl bibenzoate containing less than 2.5%by weight diethylene glycol, and preferably containing less than 1% byweight diethylene glycol.

Two processes have been found effective for the production of thedesired bis-β-hydroxy ethyl bibenzoate of this invention. In thebroadest statement, the first process produces a bis hydroxy alkylcarboxylate containing less than 2.5% by weight oxyalkyl glycol bycondensing a mixture of an aromatic dicarboxylic acid and a diol havinga carbon chain with from 2 to 8 carbon atoms at a temperature betweenabout 200° C. and about 260° C. and at a pressure between about 500 KPaand about 700 KPa. More specifically, in the first process, a mixture ofbiphenyl dicarboxylicacid and ethylene glycol is condensed at atemperature of between about 200° C. and about 260° C. and at a pressurebetween about 500 KPa and about 700 KPa. The ratio of ethylene glycol tobiphenyl dicarboxylic acid in the mixture is at least 2.0 to 2.2 molesof ethylene glycol per mole of the biphenyl dicarboxylic acid and higherratios may be used. The biphenyl dicarboxylic acid is preferably4,4'-biphenyl dicarboxylic acid. The process temperature is preferablybetween about 200° C. and about 260° C. and more preferably is about245° C. The process pressure is preferably between about 550 KPa andabout 700 KPa. Use of this process produced bis-β-hydroxy ethylbibenzoate having less than 2.5%, and often less than 1.5%, diethyleneglycol by weight as an undesirable substituent.

The second process may be stated in its broadest sense as a process forthe production of a bis hydroxy alkyl carboxylate containing less than1% by weight of oxyalkyl glycol. A mixture of an aromatic dicarboxylicacid and a diol having a carbon chain with from 2 to 8 carbon atoms iscondensed at a temperature between about 150° C. and about 250° C. andat atmospheric pressure in the presence of a catalyst selected from thegroup of catalysts based upon titanium, tin and iodine. Morespecifically, in the second process, a mixture of biphenyl dicarboxylicacid and ethylene glycol is condensed at a temperature of between about150° C. and about 200° C. and at about atmospheric pressure in thepresence of a titanium based catalyst. The biphenyl dicarboxylic acid ispreferably 4,4'-biphenyl dicarboxylic acid. The biphenyl dicarboxylicacid and the ethylene glycol are mixed with at least two moles ofethylene glycol per mole of biphenyl dicarboxylic acid, and higherratios such as, for example 4 to 1 or even 8 to 1 are preferred. Theexcess ethylene glycol is recycled during the process. The processtemperature is preferably between about 180° C. and about 200° C., andmore preferably is about 197° C., the boiling point of ethylene glycol.The process pressure is preferably about atmospheric. The catalyst ispreferably a titanium based catalyst such as the Tyzor TE® catalystproduced by E. I. duPont de Nemours & Co., Inc. Use of this processproduced bis-β-hydroxy ethyl bibenzoate having less than 1.0%, and oftenless than 0.1%, diethylene glycol by weight as an undesirablesubstituent.

The processes above have been described using the preferred4,4'-biphenyl dicarboxylic acid. However, other diacids may also be usedin the process to produce products similar to the bis-β-hydroxy ethylbibenzoate which is produced when 4,4'-biphenyl dicarboxylic acid is thestarting material. Other acceptable diacids are 3,4'-biphenyldicarboxylic acid, terephthalic acid, diphenyl ether dicarboxylic acid,stilbene dicarboxylic acid, triphenyl dicarboxylic acid, naphthalenedicarboxylic acid and other aromatic dicarboxylic acids.

It is also possible to use diols other than ethylene glycol as the otherstarting reactant in this process. Propylene glycol, butylene glycol andother alkyl diols having a carbon chain with from 3 to about 8 carbonatoms may also be used to produce compounds similar to the bis-β-hydroxyethyl bibenzoate. The use of butylene glycol, for example, will producebishydroxy butyl bibenzoate. By using other diols, it is possible toproduce two or more different bibenzoate compounds that can be used toproduce copolymers such as, for example, a copolymer of bis-β-hydroxyethyl bibenzoate and bis-hydroxy butyI bibenzoate.

A titanium based catalyst, Tyzor TE® produced by E. I. dupont deNemours& Co., Inc., was used in the process described above., Other titaniumbased catalysts such as, for example, titanium isopropoxide, may also beused. While the titanium based catalyst is preferred, Other catalystssuch as, for example, tin based catalysts such as monobutyl dihydroxytin and dibutyl tin oxide and catalysts such as tri-iodophenol may beused. The amount of catalyst used may be varied; however, as the amountof catalyst used was increased, the production of the undesireddiethylene glycol was reduced. Excess catalyst may be washed from thereaction products and used again.

It is recognized that it may be necessary to change the processconditions set out above, particularly the temperature, when thealternate reactants are used.

Use of either process to produce bis-β-hydroxy ethyl bibenzoate hasseveral advantages. The earlier use of the methyl or ethyl esters ofbiphenyl dicarboxylic acid requires extra process steps to make andpurify the ester. These steps are eliminated by the use of thedicarboxylic acid to produce the bibenzoate. In addition, elimination ofthe use of the methyl and ethyl esters of biphenyl dicarboxylic acid inother processes such as the process to make polyethylene terephthalateeliminates an impurity from the ethylene glycol so that it can berecycled without purification steps to remove methanol or ethanol. Thissimplifies the process and improves the use of raw materials by allowingfor the recycle of one of the reactants without other processing. Theprocesses of this invention also produce bis-β-hydroxy ethyl. bibenzoatehaving a smaller amount of diethylene glycol, and other undesirableimpurities, than the material produced by the processes of the prior artso that the bibenzoateois more compatible with other compounds and maymore easily be used in other manufacturing processes.

Incorporation of biphenyl dicarboxylate units into polyethyleneterephthalate leads to improvement in certain properties of thepolyethylene terephthalate such as, for example, tensile strength andmodulus and heat and weather resistance. The incorporation of thebiphenyl dicarboxylate moiety is usually achieved by condensing amixture of terephthalic acid and the methyl or ethyl ester of biphenyldicarboxylic acid with ethylene glycol. The methanol or ethanol thatresults, however, cause problems and, in addition, only a maximum of5-10% of biphenyl dicarboxylic acid may be incorporated by this method.The melt polymerization process produces polyethylene terephthalatehaving an inherent viscosity of about 0.7 and it is necessary to usesolid state polymerization in addition to melt polymerization to raisethe inherent viscosity of the polyethylene terephthalate to the range of1.1 to 1.2 that is needed for producing many products.

The addition of a few percent of biphenyl dicarboxylic acid in the formof the bis-β-hydroxy ethyl bibenzoate of this invention to thepolyethylene terephthalate raises the glass transition temperature ofthe polyethylene terephthalate. In addition, it significantly improvesthe polymerization process for polyethylene terephthalate to producepolyethylene terephthalate having an inherent viscosity of approximately1.1 to 1.2 without the previously required, and expensive, solid statepolymerization steps. Bis-β-hydroxy ethyl bibenzoate is much moresoluble than biphenyl dicarboxylic acid and it can, thus, beincorporated-into the-polyethylene terephthalate in much higher amounts.It is possible to produce a polymer of biphenyl dicarboxytic acidprepared using only bis-β-hydroxy ethyl bibenzoate having less than 2.5%by weight diethylene glycol. It is also possible to produce copolymersof biphenyl dicarboxylic acid and terephthalic acid wherein thecopolymers have from 0.1% to 99.9% by weight biphenyl dicarboxylic acidand from 99.9%. to 0.1% by weight of terephthalic acid. Preferably thecopolymers are prepared from 0.1% to 99.9% by weight bis-β-hydroxy ethylbibenzoate and from 99.1% to 0.1% by weight terephthalic acid/ethyleneglycol condensate, more preferably the copolymersoare prepared from 5%to 95% by weight bis-β-hydroxy ethyl bibenzoate and from 95% to 5% byweight terephthalic acid/ethylene glycol condensate, and even morepreferably the copolymers are prepared from 10% to70% by weightbis-β-hydroxy ethyl bibenzoate and from 90% to 30% by weightterephthalic acid/ethylene glycol condensate. The bis-β-hydroxy ethylbibenzoate preferably contains less than 2.5% by weight diethyleneglycol and more preferably contains less than 1% by weight diethyleneglycol.

The incorporation of bis-β-hydroxy ethyl bibenzoate into the productionof polyethylene terephthalate offers significant benefits. It raises theglass transition temperature and the inherent viscosity of thepolyethylene terephthalate and it allows the production of polymershaving higher molecular weights. Moreover, the use of bis-β-hydroxyethyl bibenzoate will allow the use of faster cycle times for theproduction of polyethylene terephthalate because bis-β-hydroxy ethylbibenzoate has a much higher solubility than biphenyl dicarboxylic acid,or its methyl or ethyl esters. Thus, the use of bis-β-hydroxy ethylbibenzoate offers improvement to the polymer end performance and to theprocess for the polyester production.

This invention will be explained in detail in accordance with theexamples below, which are for illustrative purposes only and shall notlimit the present invention.

EXAMPLES

In the examples below, from 2 to 8 moles of a diol, which was preferablyethylene glycol, and 1 mole of an aromatic dicarboxylic acid were mixedin a reactor under atmospheric pressure in the presence of varying typesand amounts of catalyst. The mixture was heated to a temperature withinthe range of from about 150° C. to about 250° C. and maintained at thattemperature for approximately 1 to 24 hours with water being removed.When the reaction was complete, the solution turned clear and it wasthen cooled to approximately 120° C. About 3,milliliters of a an alcoholsuch as, for example, methanol, ethanol or isopropanol, per theoreticalgram of hydroxy alkyl bibenzoate were added to crystalize the hydroxyalkyl bibenzoate and to remove any remaining diol. The reaction mass wasallowed to cool until the hydroxy alkyl bibenzoate crystallized. Thehydroxy alkyl bibenzoate was filtered, washed and dried.

EXAMPLE I

Ethylene glycol, 250 milliliters, was placed in a reactor that wasequipped with a stirrer and a heating unit. A catalyst, as shown inTable 1, and 5 grams of 4,4'-biphenyl dicarboxylic acid (BDA) were addedto the reactor. The reactor was maintained at atmospheric pressure as itwas heated to reflux at about 195° C. while being stirred continuously.The reactor was maintained at that temperature for approximately 1 to 6hours, depending upon the catalyst, with water being removed. When thereaction was complete, the solution turned clear and it was then allowedto cool to approximately ambient temperature. The product was analyzedto determine the presence of any diethylene glycol. The results areshown in Table 1.

EXAMPLE II

The process of Example I was repeated with 5 grams of terephthalic acid(TA) as the diacid. The product was analyzed to determine the presenceof any diethylene glycol. The results are shown in Table 1.

                  TABLE I                                                         ______________________________________                                                PROCESS DIETHYLENE                                                            TIME    GLYCOL CONTENT                                                CATALYST  (HRS)     IN BDA (WT %)                                                                              IN TA (WT %)                                 ______________________________________                                        Dibutyl Tin                                                                             2         0.1%         Not Detected                                 Oxide                                                                         Titanium  1.5       0.02%        Not Detected                                 Chelate                                                                       (Tyzor TE)                                                                    Tri-iodophenol                                                                          5.5       3.91%        4.9%                                         Titanium  1         <0.01%       0.06%                                        Isopropoxide                                                                  ______________________________________                                    

EXAMPLE III

A mixture of 31 grams of ethylene glycol and 61 grams of 4,4'-biphenyldicarboxylic acid was placed in a reactor which was then sealed andpurged with nitrogen four times. The reactor was initially pressurizedto approximately 480 KPa with nitrogen and heat was added to raise theinternal temperature of the reactor to approximately 240° C. After thetemperature reached about 215° C., in approximately 25 minutes, thereactants were stirred constantly. When the reactor internal temperaturereached the desired temperature of approximately 240° C., the pressurewas reduced to about 480 KPa and held relatively constant for 90minutes. Then the pressure was reduced to 350 KPa. The reaction wascontinued at these conditions for about 45 minutes at which time thepressure was reduced to atmospheric pressure and the esterificationproduct was collected. No washing or other treatment was performedbefore the product was analyzed to determine the conversion and thepresence of any diethylene glycol. The acid number was 29 mgKOH/g ofsample which corresponds to a conversion of 92%. The amount ofdiethylene glycol present was measured as 1.87% by weight. If it isdesired, the product could be washed with a solvent such as, forexample, methanol to further reduce the amount of diethylene glycolpresent.

EXAMPLE IV

The process of Example III was repeated with a mixture of 31 grams ofethylene-glycol and 42 grams of terephthalic acid prepared in thereactor. The esterification product was collected and analyzed todetermine the conversion and the presence of any diethylene glycol. Theacid number was 53 mgKOH/g of sample which corresponds to a conversionof 88.2%. The amount of diethylene glycol present was measured as 2.15%by weight.

EXAMPLE V

A mixture of 256.28 grams of ethylene glycol (4 moles) and 166.13 gramsof terephthalic acid (1 mole) was charged to a reactor with 0.54 gramsof Tyzor TE catalyst, approximately 135 parts per million (ppm) titaniumbased upon the weight of terephthalic acid charged. The reactor washeated slowly and the contents were stirred. When the reaction wasnearly complete and the solution had turned mostly clear, after about3.5 hours and at a temperature of approximately 200° C., an additional166.13 grams of terephthalic acid (1 mole) were added to the reactor.Stirring and heating were continued until the reaction was againcomplete. The reaction mass was allowed to cool until the productcrystallized. The product was analyzed to determine the presence of anydiethylene glycol. The amount of diethylene glycol remaining in theproduct was about 0.60 weight percent.

EXAMPLE VI

It is also possible to use more than one diacid in the reaction. Amixture of 248.3 grams of ethylene glycol (4 moles), 299.1 grams ofterephthalic acid (1.8 mole) and 48.5 grams of 4,4'-biphenyldicarboxylic acid (0.2 mole) were charged to a reactor with 0.65grams ofTyzor TE catalyst. The reactor was heated slowly to initiate thereaction and the contents were stirred for about 8 hours until thereaction was complete. The reaction mass was allowed to cool until theproduct crystallized. The product was analyzed to determine the presenceof any diethylene glycol. The amount of diethylene glycol remaining inthe product was about 0.50 weight percent.

EXAMPLE VII

The process of Example VI was repeated with a different catalyst. Thereactants were the same, but 0.5 gram of dibutyl tin oxide was added inplace of the Tyzor TE catalyst. The reaction took 12 hours to reachcompletion. The reaction mass was allowed to cool until the productcrystallized. The product was analyzed to determine the presence of anydiethylene glycol. The amount of diethylene glycol remaining in theproduct was about 0.89 weight percent.

EXAMPLE VIII

The process of Example VI was repeated with a different catalyst. Thereactants were the same, but 0.5 gram of antimony oxide was added inplace of the Tyzor TE catalyst. The reaction took 24 hours to reachcompletion. The reaction mass was allowed to cool until the productcrystallized. The product was analyzed to determine the presence of anydiethylene glycol. The amount of diethylene glycol remaining in theproduct was about 3.74 weight percent.

EXAMPLE IX

A mixture Of 496.6 grams of ethylene glycol (8 moles) and 242.2 grams of4,4'-biphenyl dicarboxylic acid (1 mole) were charged to a reactor with0.21 grams of Tyzor TE catalyst. The reactor was heated slowly toinitiate the reaction and the contents were stirred for about 25 hoursuntil the reaction was complete. A Sample of the unwashed product wasallowed to cool and was then analyzed to determine the presence of anydiethylene glycol. About 750 ml methanol Were added to wash the reactionmass and the reflux was continued for about 30 minutes. The reactionmass was allowed to cool until the product crystaliized. A sample of thewashed product was analyzed to determine the presence of any diethyleneglycol. The reaction time and the amount of diethylene glycol remainingin the unwashed and the washed product are shown in Table 2.

EXAMPLE X

The process of Example IX was repeated with a greater amount ofcatalyst. The reactants were the same, but 1.22 grams of the Tyzor TEcatalyst were added. The reaction took about 18.5 hours to reachcompletion. A sample of the washed product was analyzed to determine thepresence of any diethylene glycol. The reaction time and the amount ofdiethylene glycol remaining in the washed product are shown in Table 2.

EXAMPLE XI

The process of Example IX was repeated with a greater amount ofcatalyst. The reactants were the Same, but 2.33 gram of the Tyzor TEcatalyst were added. The reaction took about 12 hours to reachcompletion. A sample of the unwashed and of the washed product wasanalyzed to determine the presence of any diethylene glycol. Thereaction time and the amount of diethylene glycol remaining in theunwashed and the washed product are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                         DIETHYLENE GLYCOL CONTENT                                       CATALYST                                                                             REACTION                                                                             UNWASHED  WASHED                                         EXAMPLE                                                                              AMOUNT TIME   SAMPLE (Wt %)                                                                           SAMPLE (Wt %)                                  __________________________________________________________________________    IX     0.21 grams                                                                           25 Hrs.                                                                              1.79 wt % 0.85 wt %                                      X      1.22 grams                                                                           18.5 Hrs.                                                                            unknown   0.24 wt %                                      XI     2.33 grams                                                                           12 Hrs.                                                                              0.63 wt % 0.15 wt %                                      __________________________________________________________________________

EXAMPLE XII

A round bottom flask was filled with 18 grams of the esterificationproduct of ethylene glycol and terephthalic acid, where the molar ratiowas 1.2 to 1 respectively and the diethylene glycol content was 1.32% byweight, 2 grams of the esterification product of ethylene glycol and4,4'-biphenyl dicarboxylic acid (the bis-β-hydroxy ethyl bibenzoate ofthis invention), where the molar ratio was 2 to 1 respectively and thediethylene glycol content was 2.38% by weight, and 0.02 grams ofantimony oxide, Sb₂ O₃. The flask was fitted to a vacuum system, filledwith nitrogen, and evacuated three times to remove all oxygen. The flaskwas then placed in a salt bath preheated to 250° C. The temperature wasraised from 250° C. to 285° C. over a period of 1 hour and ethyleneglycol was distilled off. After 90 minutes at 285° C. the pressure wasreduced to 1.42 mmHg in 15 minutes. The pressure was further reducedover a period of 45 minutes to 0.20 mmHg. The reaction was continued atthese conditions for an additional 30 minutes to complete thepolymerization and the heat and vacuum were removed. The resultingpolymer had an inherent viscosity of 1.08 at a concentration of 0.5grams/deciliter in a solution of 60% phenol/40% tetrachloroethane at 25°C. The polymer had a diethylene glycol content of 1.72% by weight, andthe glass transition temperature and the melting point determined bydifferential scanning calorimeter were 83° C. and 229° C. respectively.

EXAMPLE XIII

The process of Example XII was repeated. Polymerization was conducted inthe same manner as described in Example XII except the esterificationproduct of ethylene glycol and terephthalic acid contained 3.96% byweight diethylene glycol and the bis-β-hydroxy ethyl bibenzoate alsocontained 3.96% by weight diethylene glycol. The polymer produced usingthese starting materials had an inherent viscosity of 1.09. The polymerhad a diethylene glycol content of 4.07% by weight, and the glasstransition temperature and the melting point were 78° C. and 217° C.respectively.

EXAMPLE XIV

The process of Example XII was repeated. Polymerization was conducted inthe same manner as described in Example XII except 19 grams of theesterification product of ethylene glycol and terephthalic acidcontaining 1.00% by weight diethylene glycol and 1 gram of thebis-β-hydroxy ethyl bibenzoate containing 0.15% by weight diethyleneglycol were used. The polymer produced using these starting materialshad an inherent viscosity of 1.12. The glass transition temperature was81° C.

EXAMPLE XV

A round bottom flask was filled with 6 grams of the esterificationproduct of ethylene glycol and terephthalic acid, where the molar ratiowas 1.2 to 1 respectively and the diethylene glycol content was 1.00% byweight, 14 grams of the esterification product of ethylene glycol and4,4'-biphenyl dicarboxylic acid (the bis-β-hydroxy ethyl bibenzoate ofthis invention), where the molar ratio was 2 to 1 respectively and thediethylene glycol content was 0.15% by weight, and 0.004 grams ofantimony oxide, Sb₂ O₃. The flask was fitted to a vacuum system, filledwith nitrogen, and evacuated three times to remove all oxygen. The flaskwas then placed in a salt bath preheated to 250° C. The temperature wasraised from 250° C. to 285° C. over a period of 1 hour and ethyleneglycol was distilled off. After 90 minutes at 285° C., the pressure wasreduced to 1.42 mmHg in 15 minutes. The pressure was further reducedover a period of 45 minutes to 0.20 mmHg. The reaction was continued atthese conditions for an additional 30 minutes to complete thepolymerization and the heat and vacuum were removed. The resultingpolymer had an inherent viscosity of 1.28 at a Concentration of 0.5grams/deciliter in a solution of 60% phenol/ 40% tetrachloroethane at25° C. The glass transition temperature and the melting point determinedby the differential scanning calorimeter were 111° C. and 278° C.respectively.

EXAMPLE XVI

A round bottom flask was filled with 12 grams of the esterificationproduct of ethylene glycol and terephthalic acid, where the molar ratiowas 1.2 to 1 respectively and the diethylene glycol content was 1.00% byweight, 8 grams of the esterification product of ethylene glycol and4,4'-biphenyl dicarboxylic acid (bis-β-hydroxy ethyl bibenzoate), wherethe molar ratio was 2 to 1 respectively and the diethylene glycolcontent was 0.15% by weight, and 0.004 grams of antimony oxide, Sb₂ O₃.The flask was fitted to a vacuum system, filled with nitrogen, andevacuated three times to remove all oxygen. The flask was then placed ina salt bath preheated to 250° C. The temperature was raised from 250° C.to 285° C. over a period of 1 hour and ethylene glycol was distilledoff. After 90 minutes at 285° C., the pressure was reduced to 1.42 mmHgin 15 minutes. The pressure was further reduced over a period of 45minutes to 0.20 mmHg. The reaction was continued at these conditions foran additional 30 minutes to complete the polymerization and the heat andvacuum were removed. The resulting polymer had an inherent viscosity of1.1 at a concentration of 0.5 grams/deciliter in a solution of 60%phenol/40% tetrachloroethane at 25° C. The glass transition temperaturedetermined by differential scanning calorimeter was 96° C. There was nomelting endotherm observed in the differential scanning calorimeter.

EXAMPLE XVII

A round bottom flask was filled with 20 grams of the esterificationproduct of ethylene glycol and 4,4'-biphenyl dicarboxylic acid(bis-β-hydroxyethyl bibenzoate), where the molar ratio was 2 to 1respectively and the diethylene glycol content was 0.15% by weight, and0.004 grams of antimony oxide, Sb₂ O₃. The flask was fitted to a vacuumsystem, filled with nitrogen, and evacuated three times to remove alloxygen. The flask was then placed in a salt bath preheated to 250° C.The temperature was raised from 250° C. to 292° C. over a period of 15minutes and ethylene glycol was distilled off. Within 30 minutes thetemperature was raised to 350° C. and the pressure was reduced to 0.5mmHg. The reaction was continued at these conditions for an additional15minutes to complete the polymerization and the heat and vacuum wereremoved. No glass transition temperature was observed in thedifferential scanning calorimeter. The melting point determined bydifferential scanning calorimeter was 340° C. and 229° C. respectively.

EXAMPLE XVIII

A reactor that was equipped with a stirrer and a heating unit was filledWith 120 grams of 1,4-butanediol, 50 grams of 4,4'-biphenyl dicarboxylicacid and 0.12 grams of dihydroxy butyl tin hydrochloride. The reactorwas maintained at atmospheric pressure as it was heated to reflux atabout 200° C. while being stirred continuously. The reactor wasmaintained at that temperature for approximately 40 minutes, with waterbeing removed, when a thin slurry was formed. About 10minutes later, thesolution turned clear and it was then allowed to cool to approximatelyambient temperature. The product was bis hydroxy butyl bibenzoate.

EXAMPLE XIX

A round bottom flask was filled with 8 grams of the esterificationproduct of1,4-butanediol and 4,4'-biphenyl dicarboxylic acid (bishydroxy butyl bibenzoate), where themolar ratio was 2 to 1 respectively,12 grams of the esterification product of ethylene glycol and4-4'-biphenyl dicarboxylic acid (bis-β-hydroxy ethyl bibenzoate), wherethe molar ratio was 2 to 1 respectively and the diethylene glycolcontent was 0.15% by weight, and 0.018 grams of antimony oxide, Sb₂ O₃.The flask was fitted to a vacuum system, filled with nitrogen, andevacuated three times to remove all oxygen. The flask was then placed ina salt bath preheated to 250° C. The temperature was raised from 250° C.to 285° C. over a period of 1 hour and ethylene glycol was distilledoff. After 90 minutes at 285° C., the pressure was reduced to 1.24 mmHgin 10 minutes. The pressure was further reduced over a period of 30minutes to 0.30 mmHg. The temperature was then raised to 290° C. and thepressure was reduced to 0.20 mmHg. The reaction was continued at theseconditions for an additional 45 minutes to complete the polymerizationand the heat and vacuum were then removed. The polymer had an ethyleneglycol content of 44% and a butanediol derived content of 66%. Themelting points determined by differential scanning calorimeter were 212°C. and 265° C.

We claim:
 1. A process for the production of a bis hydroxy alkylcarboxylate containing less than 2.5% by weight oxyalkyl glycolcomprising condensing a mixture of an aromatic dicarboxylic acid and adiol having a carbon chain having from 2 to 8 carbon atoms at atemperature between about 200° C. and about 260° C. and at a pressurebetween about 500 KPa and about 700 KPa in the absence of a catalyst. 2.The process of claim 1 wherein the aromatic dicarboxylic acid isselected from the group consisting of 4,4'-ciphenyl dicarboxylic acid,3,4'-biphenyl dicarboxylic acid, terephthalic acid, diphenyl etherdicarboxylic acid, stilbene dicarboxylic acid, triphenyl dicarboxylicacid, and napthalene dicarboxylic acid.
 3. The process of claim 2wherein the aromatic dicarboxylic acid is 4,4'-biphenyl dicarboxylicacid.
 4. The process of claim 1 wherein the diol has a carbon chainhaving from 2 to 4 carbon atoms.
 5. The process of claim 4 wherein thediol is ethylene glycol, propylene glycol or butylene gylcol.
 6. Theprocess of claim 5 wherein the diol is ethylene glycol.
 7. A process forthe production of bis-β-hydroxy ethyl bibenzoate containing less that2.5% by weight diethylene glycol comprising condensing a mixture of4,4'-ciphenyl dicarboxylic acid and ethylene glycol at a temperaturebetween about 200° C. and about 260° C. and at a pressure between about500 KPa and about 700 KPa in the absence of a catalyst.
 8. A polymercomprising a polyester containing bibenzoate moieties produced frombis-β-hydroxy ethyl bibenzoate having less than 2.5% by weightdiethylene glycol.
 9. The polymer of claim 8 wherein the bis-β-hydroxyethyl bibenzoate has less than 1% by weight diethylene glycol.
 10. Apolymer of biphenyl dicarboxylic acid prepared from bis-β-hydroxy ethylbibenzoate having less than 2.5% by weight diethylene glycol as themonomer.
 11. A process for the production of a bis hydroxy alkylcarboxylate containing less than 2.5% by weight oxyalkyl glycolconsisting essentially of condensing a mixture of an aromaticdicarboxylic acid and a diol having a carbon chain having from 2 to 8carbon atoms at a temperature between about 200° C. and about 260° C.and at a pressure between about 500 KPa and about 700 KPa.
 12. Theprocess of claim 11 wherein the aromatic dicarboxylic acid is selectedfrom the group consisting of 4,4'-biphenyl dicarboxylic acid,3,4'-biphenyl dicarboxylic acid, terephthalic acid, diphenyl etherdicarboxylic acid, stilebene dicarboxylic acid, triphenyl dicarboxylicacid, and naphthalene dicarboxylic acid.
 13. The process of claim 12wherein the aromatic dicarboxylic acid is 4,4'-biphenyl dicarboxylicacid.
 14. The process of claim 11 wherein the diol has a carbon chainhaving from 2 to 4 carbon atoms.
 15. The process of claim 14 wherein thediol is ethylene glycol, propylene glycol or butylene glycol.
 16. Theprocess of claim 15 wherein the diol is ethylene glycol.
 17. A processfor the production of bis-β-hydroxy ethyl bibenzoate containing lessthan 2.5% by weight diethylene glycol consisting essentially ofcondensing a mixture of 4,4'-biphenyl dicarboxylic acid and ethyleneglycol at a temperature between about 200° C. and about 260° C. and at apressure between about 500 KPa and about 700 KPa.